My Love-Hate Relationship with Cover Crops
by Herb Young, Squeeze Citrus LLCI remember the day my Romance with cover crops became a struggle. My fascination with cover crops shifted when they became a full-time job.
All of us in regenerative agriculture continually brag on cover crops. “They cover the soil, hold the moisture, reduce soil temperature and most importantly, feed microbes with those magical exudates.” Do I sound sarcastic? Well, for three years I have essentially “worked for them.”
I’m a regenerative citrus grower. I believe in all the wonderful attributes of cover crops, but I’m exhausted managing them. I went all in, believed the podcast promises. For me it meant “trunk to trunk.” I planted a beautiful ten species blend spring and another mix in the fall. The winter cover seeded in early October is beautiful; a perfect blend of three clovers, Austrian winter pea, Hairy vetch, some daikon radish, cereal rye, rape, and black oats (right). By march it’s a perfect stand, lush, fixing nitrogen, providing bee habitat, sustaining microbes. But then the growth swarms’ young trees, maybe even topping the slow growers and I don’t have a mechanism to terminate the cover crops.
Let me explain my challenges. Citrus uses microjet irrigation essentially for frost protection (tree survival). Each microjet per tree is fed from a Polytube on top of the ground. In conventional Groves this is no issue with a 12-foot-wide herbicide strip. But with trunk-to-trunk cover crops, the idea of termination without herbicides (I believe even organic herbicides would impact the microbes I’m nurturing) is nearly impossible. The above ground irrigation lines prevent mowing between trees. So, I hand-clip cover crops next to the tree and between trees. I even use an old-fashioned scythe between the trees. With all this cutting, repairing cut irrigation lines is a continuous process. How much of my “nearly full-time” grove management job involves managing cover crops? Easily 50%. Mowing parallel to the tree rows is the best chance of controlling renegade cover crops but it’s impossible to cut the last 6 inches in the row covering the irrigation line.
Summer covers have been a challenge to grow. Broadcast seeding has been brilliantly successful in wintertime but limited in summer. Scratching-in with the drag-tine gives enough soil contact to germinate but the harsh summer heat kills most of the seedlings. Each summer there was a different survivor. Year one, sunn hemp and brown top Millet had great survival. The third summer sorghum sprouted but Bermuda grass and smooth crab grass seed from the neighboring hay field dominated my grove. Some sorghum and buckwheat survive.
Even though covercrops provide many benefits but I sense they choke the trees. In a large, replicated trial comparing a conventional herbicide strip to trunk-to-trunk cover crops, the growth in the conventional (synthetic fertilizer + pesticides) trees was frustratingly twice as fast! I thought the regenerative trees just needed time to catch up… No, three years and they continue to be outpaced. I searched every reason for the faster growth and my conclusion reluctantly is that my cover crops and Bermuda grass weed compete too much with the trees. The trees may be healthy, but they are smaller. Much smaller.
Now for the positive side. The soil transformation is fantastic. In that always-covered tree row where the microbes are fed (exudates and organic nutrients through the irrigation) and all manner of roots proliferate, a penetrometer often sinks to the handles. The mulch from mowing (always blow to the row) breaks down and there’s a noticeable 2-inch rise when walking over the row. The ground is “spongy” like the experts describe. And I have aggregation (microbial buildup) on roots of trees that were pulled due to a freeze. It’s exciting to see the changes to get confirmation of a massive root system but how to manage cover crops in a grove I haven’t yet figured out. I described my relationship with cover crops as “love / hate” but it’s still the relationship I’ll stick with.